Fluoridation public health programs effectively reduce caries in children, but relatively little is known about fluoridation's effect on oral health status and dental demand among adults. Two aims of the study are: (1) to determine the effect of fluoridation on the oral health status of insured adults aged 18- 34; and (2) to determine the effect of fluoridation on dental demand among insured adults aged 18-34. Both aims are accomplished through a prospective research design. Subjects will be Washington State employees in Pullman (fluoridated) and Olympia (nonfluoridated) aged 18-34 with dental insurance from Blue Cross of Washington and Alaska. At baseline, subjects will be interviewed by telephone and receive an oral examination. Two years later Blue Cross dental claims will be collected to measure dental demand. Weighted least squares will be used to estimate fluoridation's effect on oral health. Tobit regression will be used to estimate fluoridation's effects on dental demand. Several studies report evidence suggesting that dental treatment may be inconsistent with needs, and that the relationship between need and treatment may be influenced by patient and provider factors. In Aim 3 the study's prospective design is used to determine the effect of patient and provider factors on the necessity of restorative and periodontal treatment. The dependent variable is the deviation between dental need at baseline and subsequent treatment over the prospective period. Independent variables include patient characteristics and the characteristics of dentists providing the treatment, collected through a mail survey. Logistic, OLS and Tobit regression will be used in the data analysis.